The present invention relates to devices adapted to be inserted and retained securely within the necks of bottles, such as wine bottles, medicine bottles and the like, to prevent refilling of the bottles after their original liquid contents have been decanted. Devices for preventing the refilling of bottles for reuse are known. There long has been a need for providing a safe, secure, reliable, inexpensive and practical means for preventing the refilling and reuse of bottles after their original liquid contents have been depleted. Many such devices have been patented. But so far as is presently known, none have gove into widespread commercial use. Apparently, such devices heretofore proposed and designed have not been commercially acceptable because they either are of impractical use, or too difficult or too expensive of manufacture. Examples of such prior devices are illustrated in U.S. Pat. Nos. 626,516, 787,188, 1,117,850, 1,190,408, 2,064,002, 2,380,825, 2,382,864, and 2,948,429.